Rifle bolt action

ABSTRACT

A rifle bolt action comprising a system of at least four bolt locking lugs adjacent the front thereof and corresponding receiver locking lugs. A camming arrangement is employed to cock a firing pin carried by the bolt when the bolt is rotated. A minimum angle of rotation is used to cock the firing pin while attaining a maximum locking strength for this angle of rotation due to the use of the locking lug arrangement. The forward surfaces of the receiver locking lugs are chamfered to permit slight rearward movement of the bolt over the last few degrees of rotation to unlock same, so that the spent cartridge can be broken loose.

United States Patent 91 Koon, .111.

[ 1 July 17, 1973 [73] Assignee: Firearm Development, Inc., Denton,

Tex.

[22] Filed: Apr. 7, 1971 [21] Appl. No.: 132,141

Primary Examiner-Benjamin A. Borchelt Assistant Examiner-C. T. Jordan Attorney-Thomas A. Harwood [57] ABSTRACT A rifle bolt action comprising a system of at least four bolt locking lugs adjacent the front thereof and corrcsponding receiver locking lugs. A camming arrangement is employed to cock a firing pin carried by the bolt when the bolt is rotated. A minimum angle of rotation is used to cock the firing pin while attaining a maximum locking strength for this angle of rotation due to the use of the locking lug arrangement. The forward surfaces of the receiver locking lugs are chamfered to permit slight rearward movement of the bolt over the last few degrees of rotation to unlock same, so that the spent cartridge can be broken loose.

10 Claims, 8 Drawing Figures PAIENIEU JUL 1 7 ma SHEU 1 0F 2 mm mm mm v N@ mm mm 3 3 3 i o N INVENTOR HOMER E. KOON, JR. fiQJM ATTORNEY PATENIED JUL 1 1 ma SNEHZUFZ FICELE F I 7 INVENTOR HOMER E. IKOON, JR. 7616, a ALA ATTORNEY RIFLE BOLT ACTION This invention relates to firearms, and more particularly to a bolt action rifle employing a locking lug system at the front of the bolt in which the bolt is unlocked from the receiver when the bolt is rotated to cock the firing pin.

Sales and usage of custom manufactured rifles have greatly increased in the last few years, at least in regard to the bolt action types. At the same time, competition has become more keen as to the features of the bolt action rifles offered for sale. This competition has consequently caused substantial recent innovations in bolt action rifles. For example, there is always a primary concern about safety features of firearms. In addition, the accuracy feature of rifles is important. As yet another example, efficient operation of the firearm is important.

The present invention constitutes a substantial advance in bolt action rifles in regard to the locking lug system therefor, and related camming of a cocking piece when the bolt is rotated to cock the firing pin and unlock the bolt from the receiver. The invention is primarily concerned with safety in the sense of maximum locking lug strength between the bolt and receiver, and efficient operation in cocking the firing pin when the bolt is rotated to lock same from the receiver.

Specifically, an optimum angle of rotation is utilized in rotating the bolt relative to the receiver to cock the firing pin and unlock the bolt from the receiver. To achieve this optimum angle, several factors must be considered. A cocking piece is employed to cock the firing pin, wherein the cocking piece includes a cam that rides on a cam surface in the rear wall of the bolt when the bolt is rotated. If the cam surface is too steep, too great a force is required to rotate the bolt to unlock it and cock the firing pin. At the same time, it is desirable to utilize as small an angle of rotation as possible to unlock the bolt and cock the firing pin without requiring excessive force, so that as small an angle of lift of the bolt handle as possible is required. This, of course, speeds the operation of the bolt system. It has been found that an angle of lift of form about 40 to about 55 is optimum. The maximum locking strength attainable is related to the angle of rotation, since the bolt is unlocked over substantially the same angle of m tation in which the firing pin is cocked. It is desirable, of course, to optimize both the angle of rotation and locking strength.

The locking lug system of the invention employs bolt locking lugs disposed at the front of the bolt, and corresponding receiver locking lugs for engagement therewith. A substantially continuous locking lug is provided about the front of the bolt, but which appears as an approximate square in cross-section. In a preferred embodiment, the bolt locking lug system actually comprises four locking lugs in which one locking lug ends as an adjacent one begins, thus forming the square system referred to above. There are four corresponding locking lugs depending from the receiver wall for engaging the bolt locking lugs.

In a further embodiment of the invention, the forward surfaces of the receiver locking lugs are chamfered or beveled, so that the bolt may be advanced forward over the first few degrees as it is rotated to the locked position. This permits seating of a cartridge in the chamber, and correspondingly the breaking loose of the cartridge when the bolt is unlocked.

The locking lug arrangement is also adaptable to efficient and relatively inexpensive manufacturing methods, since special forms are not required for milling or cutting of the square" locking lug arrangement.

Many other objects, features and advantages of this invention will become readily apparent from the following detailed description of a preferred embodiment thereof when taken in conjunction with the appended claims and the attached drawing wherein like reference numerals refer to like parts throughout the several figures, and in which:

FIG. 1 is a side elevational view, partly in section, of a rifle bolt mechanism utilizing the front end locking lug system of the invention;

FIG. 2 is a fragmentary bottom view of the rear portion of the bolt and a cocking piece for cocking the firing mechanism, shown with the bolt in the unlocked position;

FIG. 3 is a fragmentary bottom view of the rear portion of the bolt and the cocking piece, shown with the bolt in the locked position and the firing pin in the released, fired position;

FIG. 4 is a schematic view of the rear of the bolt illustrating the angle of rotation of the bolt between the locked and unlocked positions;

FIG. 5 is a fragmentary front perspective view of the bolt;

FIG. 6 is a fragmentary front perspective view of the receiver and receiver locking lugs;

FIG. 7 is a front elevational view, in section, showing the bolt and receiver locking lugs in the unlocked position, taken through section lines 77 of FIG. ll; and

FIG. 8 is a front elevational view, in section, of the bolt and receiver locking lugs in the locked position.

A composite view of the rifle bolt mechanism that utilizes the front end locking lugs system of the invention is shown in the side elevational view, partly in sec tion, of FIG. 1. The system includes a receiver 20 having a cylindrical bore or channel 22 extending longitudinally therein, and a cylindrical front portion 24 that is internally threaded along a length of the inner wall 26 for receiving and being secured to the threaded rear portion 28 of a barrel 30. The receiver includes a port 23 opening intermediate its ends in the top and along one side thereof through which cartridges may be loaded and unloaded. The barrel has a longitudinal bore 32 into which cartridges are chambered for firing.

A bolt 34 is carried within the cylindrical channel of the receiver for rotational and longitudinal movement therein. The bolt is rotated about a longitudinal axis as will be seen hereinafter for locking and unlocking the bolt within the receiver. The bolt is provided with a longitudinal and centrally disposed cylindrical bore 36 of a first diameter and extending the major length thereof, another smaller diameter, cylindrical bore 38 located forward of and opening into the larger diameter bore 36, and a yet smaller diameter, cylindrical bore 40 located forward of and opening into bore 38. The smallest diameter bore 40 opens into a recessed front face 42 of the bolt, wherein the butt of the cartridge is seated within this recessed face when the cartridge is chambered for firing. A firing pin assembly 44 is carried inside of the bolt and includes a cylindrical main body portion 45 having a forward portion 46 that rides within bore 38. An enlarged cylindrical shoulder 48 is disposed intermediate portions 45 and 46 against which a spring 50 abuts for urging the firing pin forward. The

firing pin mechanism also includes an integral firing pin 52 at the front end thereof that rides within bore 40 and projects forward of recessed face 42 when the mechanism is released to move to its forward-most position.

The receiver includes a plurality of inwardly extending locking lugs 54 located adjacent the front end thereof, and similarly, the bolt includes a plurality of corresponding locking lugs 56 located adjacent the front end thereof for engaging the receiver locking lugs. The bolt includes a relatively short, reduced diameter section 58 immediately behind locking lugs 56, so that the maximum diameter across the front of the bolt locking lugs is equal to the major diameter of the bolt proper. Thus the bolt and locking lug system may be withdrawn longitudinally within the cylindrical bore of the receiver. A front perspective view of the bolt and locking lugs is shown in FIG. 5, to which further reference will be had.

The main body portion 45 of the firing pin mechanism extends the length of the bore 36 of the bolt to approximately the rear face thereof, and includes a threaded extension 45' extending rearward thereof. A cocking piece 70 is threadedly secured to the rearward extension 45 and serves tocock the firing pin mechanism for firing when the bolt is rotated, all as will be explained. The cocking piece is contained within a cocking piece cover 72, wherein the cocking piece cover is loosely threaded into the rear of the bolt. More particularly, a portion 76 of the inner wall of the bolt is threaded, and the cocking piece cover includes a forwardly extending threaded portion 78 that is loosely threaded into the rear of the bolt, so that the bolt may be rotated about a longitudinal axis relative to the cocking piece cover. Although not shown, the cocking piece cover rides on the receiver surface beneath it, which prevents the cover from rotating when the bolt is rotated. The cocking piece itself bears on the inner surfaces of the cocking piece cover, and thus it is also prevented from rotation when the bolt is rotated, all as is well known.

A bolt handle 80 is secured to the bolt 34 at the rear portion thereof, and extends laterally from the side of the receiver immediately behind the rear edge 88 thereof. The'rear edge of the receiver includes a beveled portion 89 adjacent the top thereof. The bolt may be rotated along a longitudinal axis by lifting the bolt handle 80, wherein the edge portion 89 engages the body 81 of the bolt handle during the last few degrees of the rotation. When the bolt handle is raised to rotate the bolt, the bolt is unlocked by rotating the bolt locking lugs 56 to coincide with spaces between the receiver locking lugs 54, so that the bolt may then be retracted rearwardly in the receiver. On the last few degrees of rotation to unlock the bolt, the bolt handle body 81 engages edge 89 of the receiver to cause the bolt to be withdrawn a slight amount to break loose the cartridge within the chamber. As will be seen hereinafter, the construction of the locking lugs is such as to permit the slight rearward movement of the bolt over the last few degrees of rotation for unlocking it.

FIGS. 2-4 illustrate how the firing pin mechanism is cocked for firing when the bolt is rotated from the locked to the unlocked position. Both FIGS. 2 and 3 are fragmentary bottom views of the bolt and cocking piece, with FIG. 2 showing the cocking piece and firing pin mechanism in the cocked position with the bolt in the unlocked position, and FIG. 3 showing the firing pin and cocking piece in the fired position and the bolt in the locked position. As shown in FIG. 1 with the firing pin mechanism in the cocked position for firing, the cocking piece includes a portion 112 that has a front shoulder fro being engaged by a sear 110 connected to the rigger mechanism. The scar holds the cocking piece and firing pin mechanism in a retracted, cocked position until the trigger 108 is pulled. The cocking piece also includes a cam 82 that rides along a corresponding cam surface 84 formed in the rear wall of the bolt 34. The cam surface is provided by cutting an arcuate section out of the rear wall of the bolt, and the cam includes a rounded front face 83 for riding along this surface. As shown in FIG. 3, the cam is positioned at the bottom of the cam surface when the firing pin mechanism is in its most forward, fired position. As the bolt is rotated by lifting the bolt handle upward, the cocking piece 70 and firing pin mechanism attached thereto are forced rearward relative to the bolt by action of the cam riding along the cam surface. Rotation of the cocking piece during this motion is prevented by the cocking piece cover, which has surfaces along which the cocking piece 'must ride to prevent any rotation. a spent The bolt is rotated until the cam 82 of the cocking piece completely clears the cam surface 84 provided in the rear of the bolt, as shown in FIG. 2. In this embodiment, the bolt is rotated an additional 5, approximately, from where the center of the cam coincides with the beginning of the cam surface, as is schematically shown in FIG. 4, wherein it requires a rotation of approximately 45 between the positions of the cam as shown in FIG. 3 (fired position) and the position of the cam just as it clears the cam surface. The cam 82 is then resting in a slight indentation 85 in the rear wall of the bolt. The additional 5 of rotation is desirable so that the cam will be resting on a flat (or indentation 85) so that it will not slide back along the cam surface, when the bolt is longitudinally withdrawn rearward in the receiver to eject aspent cartridge.

As will be understood, the sear 110 is caused to extend upward in front of the shoulder 1 12 of the cocking piece when the cocking piece attains the position relative to the bolt as shown in FIG. 2. However, the sear cannot maintain the cocking piece and firing pin rearward when the bolt is withdrawn, and thus the necessity of the additional 5 of rotation to cock the firing pin. Then when the bolt is rotated in the opposite direction by urging the bolt handle downward so that the cam 82 is again in line with the bolt as shown in FIG. 3, but retracted relative thereto, the firing pin cannot be forced forward by the spring 50 until the trigger 108 is pulled.

Reference is now had to FIGS. 5 and 6, which are front, perspective views of the bolt and receiver, respectively, showing the locking lugs therewith. In addition, reference is also had to FIGS. 7 and 8, which are front elevational views, in section, showing the combination of the bolt and receiver locking lugs system in the unlocked and locked position, respectively. In the preferred embodiment of the invention, the receiver comprises four locking lugs 54 extending inwardly from the inner wall of the receiver with spaces provided between adjacent locking lugs. Each of the receiver locking lugs has an arcuate length along the inner wall of the receiver that subtends an angle of 77, and constitutes a segment of a circle, in cross-section, except for forward chamfered surfaces that will be discussed hereinafter. The minimum distance between opposite locking lugs 54 is just slightly greater than the diameter of the reduced diameter portion 58 of the bolt, so that the bolt may be withdrawn rearwardly in the receiver when it is unlocked.

There are four bolt locking lugs 56 that extend outwardly from the body of the bolt immediately forward of reduced diameter portion 58, each of which has two perpendicular edges 57 and 57' that terminate in a third, curved edge 91. Edge 91 conforms to the curvature of the receiver wall and is generally at an angle of 45 to edges 57 and 57'. As is seen more clearly in FIGS. 5 and 7, the four bolt locking lugs form a sub stantially square configuration as seen in the elevational view, except for the small curved edges 91. The spaces 90 between adjacent receiver locking lugs is slightly greater than the width of curved edges 91 of the bolt locking lugs, so that the bolt locking lugs pass between the receiver locking lugs when the bolt is unlocked to withdraw it within the receiver.

Referring more particularly to FIG. 6, it will be seen that each receiver locking lug 54 has chamfered or beveled surfaces 63 and 64 cut into the front face 61 and inner edge 62 thereof. Specifically, a part of the front face of the locking lug on either side of the center line thereof is cut away to provide the chamfered surfaces. Preferably, the chamfered surfaces make an angle of approximately 45 to each of face 61 and edge 62. However, the line of intersection of the chamfered surface and forward face 61 makes an angle of only about 5 with edge 62. Similarly, the line of intersection of the chamfered surface and inner edge 62 makes an angle of only about 5 with face 61.

The chamfered front surfaces of the receiver lugs permits the bolt locking lugs to partially overlap the receive lugs during the first few degress of rotating the bolt from the unlocked to the locked position, before the bolt is fully forward in the receiver. As the bolt is rotated to the closed position, it moves forwardly in the receiver as the bolt lugs ride on chamfered surfaces 63. Chamfered surfaces 64 are provided only for left handed bolts, and thus only a single chamfered surface for each receiver locking lug is required. However, both surfaces are provided to simplify manufacturing methods. The forward movement of the bolt as it is rotated to the closed position is important to firmly seat the cartridge in the firing chamber, and equally important to break the spent cartridge loose from the chamber after firing when the bolt is rotated to the unlocked position. An extractor 100 extending into the recessed face 42 fits over the rim of the shell to withdraw it with the bolt, and a spring loaded ejector pin 102 ejects the cartridge from the receiver when it clears the front edge of port 23.

The slight forward and rearward movements of the bolt as it is rotated to the locked and unlocked positions, respectively, is accomplished with much less manual effort as the bolt handle 81 rides on the beveled rear edge 89 of the receiver, than if these movements where to be attempted by only linear motion of the bolt. Thus either the receiver or bolt lugs must be chamfered to accomplish this. Chamfering of the receiver lugs, however, does not weaken the overall locking lug strength of the arrangement, since the receiver lugs can usually be made larger than the bolt lugs.

The receiver lugs are also chamfered at the rear surface by providing a concave surface 65 therein. These chamfered surfaces permit the efficient chambering of cartridges between the lugs by providing sloping sur faces on which the cartridges can ride.

To achieve the small angle of bolt handle lift, namely about 40-55, and still retain a very large locking lug strength, it is desirable that all of the circumference of the bolt be occupied by the bolt locking lugs at the forward end. At least four locking lwgs are preferably employed on each the bolt and the receiver. Utilizing less lugs and still employing a large degree of arcuate length about the bolt and receiver bolt channel generally requires an increase in the angle through which the bolt is rotated to unlock it. As mentioned before, the square configuration of the bolt locking lug system is quite strong and inexpensive to manufacture.

Although the invention has been described with ref erence to a specific embodiment thereof, certain modifications and substitutions that do not depart from the true scope thereof will undoubtedly occur to those skilled in the art. Accordingly, it is intended that the invention be limited only as defined in the appended claims.

What is claimed is:

1. In a rifle bolt action comprising a receiver having a bolt channel therein, a bolt carried within said bolt channel for sliding and rotational movement therein, said receiver having first locking lug means in said bolt channel adjacent the front thereof, said bolt having second locking lug means located adjacent the front thereof adapted to engage said first locking lug means when rotated to a locked position, a firing pin mecha nism carried by said bolt, a cocking piece attached to said firing pin mechanism and having a cam for moving on a cam surface of said bolt when said bolt is rotated from said locked position to an unlocked position to cock said firing pin mechanism, the improvement comprising:

a. said second locking lug means includes a plurality of locking lugs extending outwardly from said bolt with adjacent lugs having edges that adjoin so that said plurality of locking lugs occupy the entire circumference of the bolt portion from which they extend, and

b. said first locking lug means, said second locking lug means, said cam and said cam surface being so constructed that said second locking lug means is unlocked from said first locking lug means for sliding passage therethrough and said firing pin mechanism is cocked when said bolt is rotated of from about 40 to about 55 from the locked position.

2. In a rifle bolt action as set forth in claim 1 wherein said adjoining edges of adjacent lugs lie in the same plane.

3. in a rifle bolt action as set forth in claim 2 wherein there are a total of four of said plurality of locking lugs of said second locking lug means, so that said second locking lug means has a substantially square configuration in front, elevational view.

4. In a rifle bolt action as set forth in claim l wherein said first locking lug means includes a plurality of looking lugs extending inwardly from the wall of said bolt channel, each having a part of the front surface thereof chamfered, so that said bolt may be advanced forwardly as said bolt is rotated from an unlocked position to said locked position.

5. In a rifle bolt action as set forth in claim 1 wherein said bolt has a length adjacent the front end thereof of diameter smaller than the diameter of the major portion of said bolt, and said plurality of locking lugs of said second locking lug means extends outwardly from said length of smaller diameter.

6. In a rifle bolt action as set forth in claim wherein said adjoining edges of adjacent lugs lie in a plane that is tangential to the surface of said length of smaller diameter.

7. In a rifle bolt action as set forth in claim 1 wherein said first locking lug means includes a plurality of locking lugs extending inwardly from the wall of said bolt channel, with spaces between adjacent lugs to permit the longitudinal passage of said locking lugs of said second locking lug means therethrough when said bolt is rotated from said locked position to an unlocked position.

8. In a rifle bolt action as set forth in claim 1 wherein said first locking lug means includes a plurality of locking lugs extending inwardly from the wall of said bolt channel, said plurality of locking lugs of said first locking lug means being equal in number to said plurality of locking lugs of said second locking lug means, with the forward surfaces of all of said plurality of locking lugs of said first locking lug means lying in a single plane, and the rearward surfaces of all of said plurality of locking lugs of said second locking lug means lying in a single plane.

9. In a rifle bolt action as set forth in claim 3 wherein said first locking lug means includes four locking lugs extending inwardly from the wall of said bolt channel, with spaces between adjacent lugs to permit the longitudinal passage of said locking lugs of said second locking lug means therethrough when said bolt is rotated from said locked position to an unlocked position.

10. In a rifle bolt action as set forth in claim 9 wherein each of said plurality of locking lugs of said first locking lug means has a part of the front surface chamfered, so that said bolt may be advanced forwardly as said bolt is rotated from said unlocked position to said locked position.

* III 

1. In a rifle bolt action comprising a receiver having a bolt channel therein, a bolt carried within said bolt channel for sliding and rotational movement therein, said receiver having first locking lug means in said bolt channel adjacent the front thereof, said bolt having second locking lug means located adjacent the front thereof adapted to engage said first locking lug means when rotated to a locked position, a firing pin mechanism carried by said bolt, a cocking piece attached to said firing pin mechanism and having a cam for moving on a cam surface of said bolt when said bolt is rotated from said locked position to an unlocked position to cock said firing pin mechanism, the improvement comprising: a. said second locking lug means includes a plurality of locking lugs extending outwardly from said bolt with adjacent lugs having edges that adjoin so that said plurality of locking lugs occupy the entire circumference of the bolt portion from which they extend, and b. said first locking lug means, said second locking lug means, said cam and said cam surface being so constructed that said second locking lug means is unlocked from said first locking lug means for sliding passage therethrough and said firing pin mechanism is cocked when said bolt is rotated of from about 40* to about 55* from the locked position.
 2. In a rifle bolt action as set forth in claim 1 wherein said adjoining edges of adjacent lugs lie in the same plane.
 3. In a rifle bolt action as set forth in claim 2 wherein there are a total of four of said plurality of locking lugs of said second locking lug means, so that said second locking lug means has a substantially square configuration in front, elevational view.
 4. In a rifle bolt action as set forth in claim 1 wherein said first locking lug means includes a plurality of locking lugs extending inwardly from the wall of said bolt channel, each having a part of the front surface thereof chamfered, so that said bolt may be advanced forwardly as said bolt is rotated from an unlocked position to said locked position.
 5. In a rifle bolt action as set forth in claim 1 wherein said bolt has a length adjacent the front end thereof of diameter smaller than the diameter of the major portion of said bolt, and said plurality of locking lugs of said second locking lug means extends outwardly from said length of smaller diameter.
 6. In a rifle bolt action as set forth in claim 5 wherein said adjoining edges of adjacent lugs lie in a plane that is tangential to the surface of said length of smaller diameter.
 7. In a rifle bolt action as set forth in claim 1 wherein said first locking lug means includes a plurality of locking lugs extending inwardly from the wall of said bolt channel, with spaces between adjacent lugs to permit the longitudinal passage of said locking lugs of said second locking lug means therethrough when said bolt is rotated from said locked position to an unlocked position.
 8. In a rifle bolt action as set forth in claim 1 wherein said first locking lug means includes a plurality of locking lugs extending inwardly from the wall of said bolt channel, said plurality of locking lugs of said first locking lug means being equal in number to said plurality of locking lugs of said second locking lug means, with the forward surfaces of all of said plurality of locking lugs of said first locking lug means lying in a single plane, and the rearward surfaces of all of said plurality of locking lugs of said second locking lug means lying in a single plane.
 9. In a rifle bolt action as set forth in claim 3 wherein said first locking lug means includes four locking lugs extending inwardly from the wall of said bolt channel, with spaces between adjacent lugs to permit the longitudinal passage of said locking lugs of said second locking lUg means therethrough when said bolt is rotated from said locked position to an unlocked position.
 10. In a rifle bolt action as set forth in claim 9 wherein each of said plurality of locking lugs of said first locking lug means has a part of the front surface chamfered, so that said bolt may be advanced forwardly as said bolt is rotated from said unlocked position to said locked position. 